Molasses can be used in a hydro setup and provide similar benefits as in soil, but it must be used correctly.
Molasses is an organic substance, which means it is not available for roots to uptake until it has been broken down. Idealy, it will be broken down by beneficial microbes, and then becomes chemical fertilizer. Synthetic bud sweetener is the same thing, it's just already available in chemical form.
So if you want to use molasses in any hydro set up, you should make sure it mixes thoroughly and then add in some beneficial bacteria and fungi. You can buy bottled products or brew an EWC tea. The reason higher temps can cause problems after adding molasses is, microbes breed faster in warm water. If you don't add beneficial microbes, you are setting up a perfect environment for harmful pathogens.